1. Field of the Invention
The present invention relates to a thin film transistor substrate and a method of producing the same and, more particularly, to a thin film transistor substrate that has reduced production cost and defect rate and a method of producing the same pixel electrode.
2. Description of Related Art
A liquid crystal display includes two substrates and a liquid crystal layer that is interposed between the two substrates. One of the two substrates is a thin film transistor substrate. In the thin film transistor substrate, a plurality of wiring lines is formed on an insulating substrate. A representative example of a process of forming wiring lines includes a photolithography process in which constituent substances are layered and patterned using a mask process. However, since the photolithography process includes numerous processes such as deposition of thin film, application of a photoresist, alignment of a mask, exposing, developing, etching, and stripping, the process time is long and product cost is high.
A lift-off process has been used to reduce the number of mask processes. In a lift-off process, when a passivation layer and a pixel electrode of a thin film transistor substrate are used, the passivation layer is patterned using a photoresist pattern, a conductive substance is layered on the entire substrate surface, and the photoresist pattern and some of the conductive substance for the pixel electrode that is provided on the photoresist pattern are simultaneously removed using a stripper to form the pixel electrode.
To remove the photoresist pattern and an upper surface that is coated with the conductive substance, the stripper is brought into contact with a lateral surface or a lower surface of the photoresist pattern. In connection with this, a contact area of the stripper and the photoresist pattern must be large enough to prevent the formation of unacceptable patterns resulting from the remaining photoresist pattern. That is, it is required that the passivation layer, which is provided under the photoresist pattern, be overetched to form desirable undercuts in the photoresist pattern. It is also required that step coverage of the conductive substance for the pixel electrode, which is provided on the photoresist pattern, is not very high. Meanwhile, in the lift-off process, since the stripper is frequently reused, defects may form on the thin film transistor substrate when the conductive substance for the pixel electrode remains in the stripper undissolved. In addition, since the conductive substance for the pixel electrode is removed during the lift-off process, reduction in the production cost of the thin film transistor substrate may be affected.
Accordingly, there remains a need to develop a thin film transistor substrate using a conductive substance for a pixel electrode that has desirable step coverage, and can desirably dissolve in a stripper to improve the lift off performance at a reduced cost.